Canberra in September 2012: Hot days and cold nights

Rainfall - Wettest September day since 2002

Canberra Airport recorded 41.4 mm of rainfall during September, below the historical average of 52 mm. The rain fell over 9 days, close to the September average of 10 days, but only one day recorded more than 5 mm (average 3 days), the fewest since 2007. Almost all of the rain fell as a cold front produced rain and thunderstorms in the ACT on the 29th, with up to 48.8 mm at Mt Ginini, while Canberra Airport recorded its wettest September day since 2002 with 28.4 mm.

Temperature - Warm days and cold nights

The average maximum temperature at Canberra Airport was 18 °C, 1.8 °C above the historical average. This is the equal 6th warmest September on record for Canberra, but slightly cooler than 18.2 °C in 2011. The warm days were associated with generally dry, sunny conditions during the month; eighteen days reached 18 °C or higher, the third highest on record for Canberra.

In contrast, the average minimum temperature was 1.6 °C, 1.7 °C below the historical record and the coldest Semptember since 1994. The cool nights were also associated with clear conditions, with eight nights falling below -2 °C during the month, the second highest on record following 9 cold nights in 1971 and 1946 (average 2 nights). Nights were particularly cold at the start of the month, reaching -6.8 °C on the 1st, the coldest September night on record for Canberra, with three consecutive nights falling below -4 °C. This is the latest such spell on record, with the previous record almost two weeks earlier in 22-24 August 1978.

Other phenomena

The prevailing wind direction at Canberra Airport was northwesterly, with 76% of 3pm winds between WNW and NNW, normal for September. There were four strong wind days reported at the airport, with a maximum wind gust of 80 km/hr on the 5th. Canberra Airport recorded an average of 8.0 hours of bright sunshine, slightly above the historical average of 7.7 hours, with two thunderstorms reported in the ACT on the 18th and 28th.

Notes

As of March 2010, the official station for Canberra is 70351 'Canberra Airport'. Averages from the previous site, 70014 Canberra Airport Comparison, are used for comparisons (all years of record).

A Monthly Climate Summary is prepared to list the main features of the weather in ACT Monthly Summary using the most timely and accurate information available on the date of publication; it will generally not be updated. Later information, including data that has had greater opportunity for quality control, will be presented in the Monthly Weather Review, usually published in the fourth week of the month.

This statement has been prepared based on information available at
9 am on Tuesday 2 October 2012.
Some checks have been made on the data, but it is possible that results will change
as new information becomes available.

Averages are long-term means based on observations from
all available years of record, which vary widely from site to site.
They are not shown for sites with less than 20 years of record, as they cannot then be calculated reliably.
The median
is sometimes more representative than the
mean
of long-term average rain.

The Rank indicates how rainfall this time compares with the climate record for the site,
based on the
decile ranking
(very low rainfall is in decile 1, low in decile 2 or 3,
average in decile 4 to 7, high in decile 8 or 9
and very high is in decile 10).
The Fraction of average shows how much rain has fallen this time as a
percentage of the long-term mean.